A hybrid vehicle that uses both a motor and engine for driving the wheels are now attracting attention as ecologically-friendly vehicles. Research on a configuration allowing charging from an external source for such hybrid vehicles is in progress. This is advantageous in that the number of times the driver has to go to a gas station to supply fuel is reduced by conducting charging at the residence and the like. There is also an advantage in terms of cost by using economic midnight power.
Japanese Patent Laying-Open No. 8-37703 discloses a hybrid vehicle including a battery that can be charged by external charge means, an electric motor that can drive the wheels based on the electric power from the battery, an engine used to drive the wheels, and control means for controlling the operation of the electric motor and engine.
By frequently charging the battery from an external power supply based on such a configuration that allows charging from an external power supply for the vehicle, the frequency of operating the engine can be reduced by maintaining the SOC (State of Charge) of the battery constantly at a favorable level. It is possible to envisage an event of such charging operation in the case where the cost required for charging through external electric power is lower than the cost of fuel required to operate the engine.
It is noted that, when the engine is left without being operated for a long period of time, fuel vapor will be generated significantly if the temperature is high. For example, a great amount of evaporating gas of gasoline will be generated in the gasoline tank in the case where a gasoline engine is employed. If the amount of evaporating gas is so great that it cannot be trapped by a charcoal canister or the like, the evaporating gas will be discharged into the air, which departs from the initial object of the hybrid vehicle to realize low pollution.
A possible approach to this problem is to force the canister to be heated by means of a heater or the like during the running operation to conduct a purge intentionally for the purpose of mixing the fuel vapor with the intake air to cause combustion. However, the value of the vehicle will be degraded if the EV allowed travel distance is reduced by the power consumption of the heater.